In the Options tab there is a Save button that saves the configuration. Once you have done that and restart KStars the value should be used. On my Raspberry Pis (yes, more than one) changes the settings sometimes aren't picked up immediately and require one or more reboots.
Thanks again for your time and patience.
Yes, I missed the save buried in the config tab. DUH. Should have been more patient.
AFAICT, the changes are written to, in my case:
~/.indi/ZWO CCD ASI120MM_config.xml
with the default values at:
~/.indi/ZWO CCD ASI120MM_config.default.xml
Here's hoping I did no permanent damage elsewhere by editing the former...
Cheers